From a recent discussion here at D-series.org:
klungemonger
Posted: Mon Nov 10, 2003 9:14 pm Post subject: Y8 vs. Z6 vs. Y7 heads...
OK, I was liking the info on the old board about the differences in intake tracts on the Y8 and Z6. My question is: which one does the Y7 take after? All I know is it has the same size combustion chamber as teh Z6, but does it have the symmetrical intake ports like the Z6 or is it modeled after the Y8 head? Although as the old posts mentioned, on lower hp applications the difference may not be apparent. I'm just doing an all-motor 11:1 c/r Y7 buildup...
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Guest500
Posted: Tue Nov 11, 2003 2:49 am Post subject:
the y7 is the same casting as the y8. the y7 and z6 heads have the same volume, which is more than that of the y8.

Klung, you want to refresh me and others on the differences between the z6 and 78 intake tracks and combustion chambers?
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Hondadog
Posted: Tue Nov 11, 2003 5:33 am Post subject:
Hell yeah. Klunge how are you? I would love to hear about it. When I put a y7 head on my last project the combustion chambers did look different.
Like Guest500 said the y7's larger 34.6 cc chambers vs. the y8's 32.8 .
Also, the chamber shape. The y8's chambers are squared off towards the ports and the y7's are round. y7 looked symmetrical to me.

The y8 and y7 have the same valve sizes though. As for the intake port lengths though I am not sure. Enlighten me.

klungemonger
Posted: Tue Nov 11, 2003 1:03 pm Post subject:
What's up dudes. kommon_sense has a link in his sig on SHO that directs you to the old d-series.org board (which you can't post on but can still read.) It has pics and stuff and a description of the difference between the intake port shape.

Basically says the Y8 makes more power lower in teh range due to better swirl &amp; combustion efficiency, but when you're going all out the Z6 ends up better for hp due to better top end flow capability. The Z6 has symmetrical intake tracts, the Y8 has curved/shaped ports where the left/right for each cylinder are different from each other.
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Toddnos
Posted: Tue Nov 11, 2003 10:19 pm Post subject:
klungemonger wrote:
What's up dudes. kommon_sense has a link in his sig on SHO that directs you to the old d-series.org board (which you can't post on but can still read.) It has pics and stuff and a description of the difference between the intake port shape.

Basically says the Y8 makes more power lower in teh range due to better swirl &amp; combustion efficiency, but when you're going all out the Z6 ends up better for hp due to better top end flow capability. The Z6 has symmetrical intake tracts, the Y8 has curved/shaped ports where the left/right for each cylinder are different from each other.
But with a slight port and deshrouded valves, the y8 will flow superior to the z6 or y7.............
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TeamDragonSpeed
Posted: Wed Nov 12, 2003 1:28 am Post subject:
I got into this discussion a while back. Basically the PnP work changes the flow efficency but not the flow characteristics. Or in other words the z6 head still better up top.
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Toddnos
Posted: Wed Nov 12, 2003 1:49 pm Post subject:
TeamDragonSpeed wrote:
I got into this discussion a while back. Basically the PnP work changes the flow efficency but not the flow characteristics. Or in other words the z6 head still better up top.
Ive read/heard differently........oh well
_________________
Not a substitute for actual human contact.
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klungemonger
Posted: Wed Nov 12, 2003 2:39 pm Post subject:
Toddnos wrote:
But with a slight port and deshrouded valves, the y8 will flow superior to the z6 or y7....

I fail to see how grinding in the chamber will improve flow through the ports...they are designed to direct more air through one valve than the other. Massive recongifuration of the runners seems to be the solution. Sharpen up that carbide bit...
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krAzySi
Posted: Wed Nov 12, 2003 6:15 pm Post subject:
Guest500 wrote:
the y7 is the same casting as the y8. the y7 and z6 heads have the same volume, which is more than that of the y8.

just curious and kinda OT....can u swap the y8 valvetrain on the y7 head since it has the same casting?
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klungemonger
Posted: Wed Nov 12, 2003 6:45 pm Post subject:
krAzySi wrote:
Guest500 wrote:
the y7 is the same casting as the y8. the y7 and z6 heads have the same volume, which is more than that of the y8.

just curious and kinda OT....can u swap the y8 valvetrain on the y7 head since it has the same casting?

I wondered the same thing. I think it would fit but the VTEC solenoid mount and proper oil passages aren't machined onto a Y7 casting I don't think. Someone enlighten me if you know different...
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Hondadog
Posted: Wed Nov 12, 2003 6:47 pm Post subject:
Good question. I had a ? kind of like that about using the y5 roller rockers in the y7 head. I have heard that the y5/7/8 between 96-98 Were the same castings except of course the chamber design/cc's, valvetrain.
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klungemonger
Posted: Wed Nov 12, 2003 7:13 pm Post subject:
Hondadog wrote:
Good question. I had a ? kind of like that about using the y5 roller rockers in the y7 head. I have heard that the y5/7/8 between 96-98 Were the same castings except of course the chamber design/cc's, valvetrain.

I doubt there are any compatible valvetrain parts, especially from VTEC to non-VTEC. I suppose it's possible maybe on the exhaust side, but probably not with intake side.
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I fail to see how grinding in the chamber will improve flow through the ports...they are designed to direct more air through one valve than the other. Massive recongifuration of the runners seems to be the solution. Sharpen up that carbide bit...
which valves are getting more air?? would this affect nitrous use? I only wonder, because i have had a few things go wrong under nitrous conditions with my y8 head.......blown #2 exhaust valve.......50 lbs lower comp. in the #3....
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Not a substitute for actual human contact.
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klungemonger
Posted: Wed Nov 12, 2003 8:40 pm Post subject:
Toddnos wrote:
which valves are getting more air?? would this affect nitrous use? I only wonder, because i have had a few things go wrong under nitrous conditions with my y8 head.......blown #2 exhaust valve.......50 lbs lower comp. in the #3....

I don't think so. Typically nitrous ruins stuff due to lack of enough fuel, or failure to retard timing to prevent detonation. Nitrous can burn stuff like valves and rings. IT doesn't require any special flow to be delivered properly, since it doesn't increase the volume of air going into the cylinders, only the percentage of oxygen.
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Toddnos
Posted: Thu Nov 13, 2003 1:16 pm Post subject:
klungemonger wrote:
Toddnos wrote:
which valves are getting more air?? would this affect nitrous use? I only wonder, because i have had a few things go wrong under nitrous conditions with my y8 head.......blown #2 exhaust valve.......50 lbs lower comp. in the #3....

I don't think so. Typically nitrous ruins stuff due to lack of enough fuel, or failure to retard timing to prevent detonation. Nitrous can burn stuff like valves and rings. IT doesn't require any special flow to be delivered properly, since it doesn't increase the volume of air going into the cylinders, only the percentage of oxygen.
Word.....thats what i thought.......But which cylinders are getting more air with the y8 head?
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klungemonger
Posted: Thu Nov 13, 2003 1:23 pm Post subject:
Toddnos wrote:
Word.....thats what i thought.......But which cylinders are getting more air with the y8 head?

Ah, now I see what you're getting at. The cylinders are all getting the same amount of air, the uneven runners are in each cylinder. The intake port configuration of each cylinder is the same, there are 2 ports that split off inside the main intake port of each cylinder, the issue is that all the left intake ports have a certain shape while the right side has another. It's to create a high-swirl condition in the chamber which atomizes fuel better and gives more economy. But for high hp you want volume and velocity, not swirl, so in that instance you'd want 2 even high-flowing ports.
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Ah, now I see what you're getting at. The cylinders are all getting the same amount of air, the uneven runners are in each cylinder. The intake port configuration of each cylinder is the same, there are 2 ports that split off inside the main intake port of each cylinder, the issue is that all the left intake ports have a certain shape while the right side has another. It's to create a high-swirl condition in the chamber which atomizes fuel better and gives more economy. But for high hp you want volume and velocity, not swirl, so in that instance you'd want 2 even high-flowing ports.

OK i see..........I had my head ported, by a guy that used to work for PYR racing.......I think he match ported the smaller runner to the bigger one.........I need to know if he widened the other runner as well.....He said it was mildly done.....

ZEX Man
Registered User
Posts: 267
(3/19/03 6:58 pm)
heads Bottom line.....I lost 30 hp peak on my 400hp race motor by switching from an unported Z6 head to a ported Y8 head. The engine made great power below 5500, but died up top. In fact, it made 40 more hp below 5500. The Z6 ports are symetrical and provide a much better quality of flow at high engine speeds.

Noahk
Registered User
Posts: 24
(3/20/03 2:08 pm)
ZEX Man Can the Y8 head be correct to flow as well as the z6 on the top end? Is it that the Y8 ports are different width and shape? Wouldn't you correct this when you port the head? Thanks for the info!

chivic
Registered User
Posts: 36
(3/20/03 4:14 pm)
symmetry what is symetrical about the ports? im not catching your drift. Also if i want to focus on more mid range power would it be beneficial to swap the y8 on? if so what mods do i have to do for the distributor?

Tetsuo71
Registered User
Posts: 8
(3/23/03 7:21 am)
Re: Z6 vs Y8 I have 2 question for ZEX: What manifold and pistons were you running with that Y8 head? Did you change either when you switched heads? Just curious.

As you can see from the pictures above, there are a few significant differences between the Y8 and Z6 head, the most important being the different shaped combustion chambers and the different shape and length of the intake port dividers.
The loss of horsepower ZEXman saw with the Y8 head is a result of the curved intake divider, which is designed to create better low velocity air swirl and improved fuel economy. But as ZEXman points out, it does cause a loss of high rpm horsepower on heavily developed naturally aspirated or forced induction engines like his. However, the divider can be straightened out very easily with basic porting tools, which is exactly what I've done on my Y8 head. I will post pictures of this once I get the head back from the shop (I'm having a 3 angle valve job done). Point being, this design limitation of the Y8 head can be corrected, or at least so the story goes. I have yet to actually test this idea, but Moose and I will be flow benching our heads -- his is a ported Z6 and mine is a ported Y8. We did the port jobs ourselves so they are very similar and we'll flow bench them at the same shop so the results are comparable. Should be interesting to see how things turn out! If my Y8 head performs as well as Moose's Z6 head both on the flow bench, at the dyno, and at the race track, we'll have some pretty strong evidence that the Y8 head divider issue is easily addressed. And of course the higher compression Y8 head, due to the squared off combustion chamber design with larger quench pads, is a clear advantage if you're looking to raise compression easily and safely.

ZEX Man
Registered User
Posts: 270
(3/23/03 6:06 pm)
build Maxzee,

If you back up from the Y8 divider and look at the entire port, you will see how the port is curved. The center divider simply blends with the shape of the port. You will never see a good race head curved in this manner. The high flow air quality is very poor. The curved ports are great for emissions and power below 5000 rpm. When was the last time you raced someone and spent much time below 5000rpm? To correct the Y8 port, it would require a great deal of grinding and epoxy filling. It is much easier to simply port the Z6 and mill the head to get the compression you want. The whole quench pad deal is really important when you are running large amounts of cylinder pressure and trying to control detonation. On a mild (250hp and less) motor, you need to concentrate on the basics.....good airflow and the correct compression ratio. Also, if you really want to do it easy, just open up the combustion chamber on the Z6 head, to the quench pads, by the diameter of your engine's bore. Order a set of pistons from JE with .090 higher pin height and you will have the best of both worlds with a minimal amount of effort. A good quench pad with .035-040 clearance and the best D-series ports out there. I built a N/A motor like this and in a 2150 lb. CRX with a 100hp shot of nitrous, it ran 12.50s at 109mph.

Later,

ZEX Man

ZEX Man
Registered User
Posts: 271
(3/23/03 6:20 pm)
combo Tetsuo71,

I was using a Z6 manifold on both the Y8 head the Z6 head. Custom made pistons for both heads, both 9-1 compression.

Later,

ZEX Man

Maxzee
Registered User
Posts: 86
(3/23/03 9:45 pm)
Re: combo ZEXman, you raise an interesting point about the entire port being curved, rather than just the divider. I have not noticed this on my Y8 head, but then I haven't looked at it from the more distant perspective you've suggested. Very interesting stuff. You're the first to mention this in any discussions I've had about the Y8 head. I'll certainly take a renewed look at the Y8 head compared to the Z6 head. But for now I'll still cling to the hope that all those hours ported my Y8 head and straightening out the divider wasn't a waste Perhaps on my moderate naturally aspirated engine build it won't be as big an issue as on your 400hp turbo/nitrous beast. I'll certainly post the results of our flowbench and dyno tests up here once we've done them.

ryancivic2000
Registered User
Posts: 175
(3/24/03 5:16 pm)
Re: combo This is turning out to be a real good post. Very informative.

ryancivic2000
Registered User
Posts: 176
(3/24/03 5:17 pm)
Re: combo This is turning out to be a real good post. Very informative. I can't wait to see the flow bench and dyno results go. Does anyone have flow results in stock form? This would be interesting to see as well.

Maxzee
Registered User
Posts: 88
(3/24/03 6:12 pm)
Re: combo ryan, I posted stock flowbench numbers for a Y8 given to me by Joe Alaniz in this thread over in the Naturally Aspirated forum:

pub143.ezboard.com/fhonda...1931.topic

I don't have stock flowbench numbers for a Z6 head yet, but Moose has a spare Z6 head I think, so perhaps we'll flowbench it to compare to his ported Z6 head.

We'll post the results once the heads have been flowed. Should be in the next few weeks I think.

Maxzee
Registered User
Posts: 89
(3/25/03 1:15 pm)
Re: combo Me too! Problem is, there doesn't seem to be much evidence of quality vs quantity in the whole Z6 or Y8 head debate, ZEXman's experience aside. His engine is putting out such extreme power numbers that I'm not really sure how applicable his results are for naturally aspirated engines like the ones Moose and I are building. Pefectionist519 has flowbenched his ported Y8 head and his numbers match up very well with flowbenched ported Z6 head results Tom from PortFlow sent me. Of course comparing data from one flowbench to another is like comparing data from one dyno to another, so that's why Moose and I are so curious to see how our heads compare on the same flowbench and with the same quality (ie. DIY) port and polish job.

It's incremental knowledge, like everything else. Hopefully we can contribute our own tiny piece of useful data to the discussion soon.

Cheers,
Maxzee

Tetsuo71
Registered User
Posts: 14
(3/25/03 4:55 pm)
Re: Z6 vs Y8 Thank you for all the input on this topic. Alot to digest, huh? I'm still processing the information.

Would it be ridiculous of me to assume, then, that for a daily driver type machine, the Y8 would be the much better choice? Shouldn't the curvature of the ports and resultant better mixing of the air and fuel translate into much more favorable bottom-end torque characteristics?

I'm building up a Y8 head right now for a lightly-built daily driver, and while better top-end power would be nice, I'd much rather have a little more "under the curve" than a few more peak.

Maxzee
Registered User
Posts: 92
(3/30/03 7:39 pm)
Re: Awesome! It's true that our discuss so far has focused on maximum horsepower extraction, since that's what most of us here are interested in for our motorsport drug of choice.

In stock or near stock form, I wouldn't say the Y8 is a much better design than the Z6, perhaps marginally so depending on your perspective. The Y8 head does, for example, produce better low to mid rpm fuel atomization from what I'm told, but the Z6 breaths more freely at high rpm.

Put it this way, if you threw a D16Z6-powered car and D16Y8-powered car on the dyno the shape of their respective horsepower and torque curves would be very very similar. It's not until you get up into some pretty extreme horsepower levels like 'Bisi and ZEXman are achieving that you'll start to see the differences in design leave their signatures on the power and torque curves.
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Comment
Rydaddy
Registered User
Posts: 17
(6/1/03 10:24 am)
Comparison? So what's up with that comparison of the two heads on the flowbench Maxzee? I would be interested to know, since I just sold my y8 head in favor of a ported z6 head for my new motor. This thread helped me change my mind - hope it was worth it!

civsick
Registered User
Posts: 788
(6/1/03 12:07 pm)
battle of the heads! I just wanted to say thanks guys, this has been really intriging thus far! I'm not trying to debate which head is better, but I did lean towards the y8 head do to my High compression all motor project. The quench pad area of the head was ideal to me since the project motor is going to produce a compression ratio over 13.1:1 and like many members on the board My build is on a tight budget, so exspenses spent on machine work is definitly an issue for me as well.

Maxzee I'm definitly curious about the flowbench test between both your y8 and Mooses Z6, since I'm also going to attempt an @ home P/P job. Part of my main concentration is going to be on the intake side of the head and getting the bowls cleanup and polished to further atribute to the antidedonation characteristics of the y8 head.

Also I truely respect everyones opinion on this board, becuase it truely lets me get to understand both sides of everything. Zexman said he lost 30 peak hp, but had a gain of 40 hp below 5500 rpm, so I'm curious on what the differences in time slips were. A 40 hp gain down low is still a killer gain. I'm wondering about how much more torque the y8 head can produce down low compared to the z6, since hondas aren't known for producing torque in the lower rpm range. Also W/ Zex mans build, would a different cam profile correct some of the peak hp loss w/ the y8 head?

Rydaddy
Registered User
Posts: 19
(6/1/03 2:50 pm)
. It seems doubtful that a cam could correct for peak hp. The shape of the intake tracts (curved on the y8 rather than straight thru on the z6) accounts for the loss up top. The same cam in both heads would probably leave the same amount to be desired.

pearlsixtytwo
Registered User
Posts: 56
(6/1/03 9:09 pm)

Intakes? No one mentioned which intake was better, the Y8 or Z6? Anyone?

SinnerSol
Registered User
Posts: 78
(6/2/03 6:48 am)
yup I came to this message as a referance to see which IM is better? I'm going to be doing another swap tonight and I have both so which should I use?

From what I've 'heard' is that the d16y8 IM is the 'type-r' manifold for the dseries since its so big. I heard this a few times. I bet a search would be the best thing to do.

Nick

Bizzar
Registered User
Posts: 138
(6/2/03 9:25 am)

Re: yup So in theory a Y8 would work better in a supercharged application? The SC will take care of that low end torque no? I want to begin building a Z6 part by part but with all this great info over here at D series I often find myself torn on decisions decisions....I lean more towards the Z6 because it is cheaper to find a block/head combo rather than block separate and y8 head. I am also looking for lower comp but that can always be done with head gaskets and pistons rather than the head for simplicity matters. BAH!!! I still can't decide. I think I will just go with the Z6 because intake has no bearing with a SC...unless of course I do a somewhat AKSC type setup with a custom intake and intercooled. Bone?? your thoughts on which head to go with a supercharged engine? Z6 bottom end.

pearlsixtytwo
Registered User
Posts: 58
(6/2/03 1:32 pm)

Re: Intake... I've tried searching this site, and nothing comes up answering which intake is better, the Z6 or Y8.

PRcivicHB
Registered User
Posts: 2
(6/2/03 10:59 pm)
INTAKE MANI I read somewhere the Y8 Intake mani is better because of the short and Fat runners...

Y8 head with professional 3 angle valve job and DIY porting - improved flow by 7-8% across the board with max corrected flow in the 205 cfm range at max lift.

Z6 head with professional 3 angle valve job and DIY porting - improved flow by 5-6% across the board with max corrected flow in the 210 cfm range at max lift.

What's interesting about these results is that although we got more improvement over stock flow numbers with the Y8 head (we did spend more time on this head, particularly with regards to trying to straighten out the port divider on the intake side), the Z6 head still flowed better across the board. What this indicates, at least in my mind, is that the Z6 is a better starting point for a basic DIY porting job and for most street set-ups. Only if you plan to run high compression does the Y8 start to become an interesting option, given it's "closed" or square design combustion chamber with quench pads. But be prepared to spend more time porting the Y8 head to get it to flow as well as the Z6 head.

Maxzee
Registered User
Posts: 110
(6/4/03 12:42 pm)
Re: INTAKE MANI nope, we didn't flow them when stock, but the shop that flowed them for us has flowed many stock Z6 and Y8 heads so he gave us stock numbers to compare to. On his Australian flowbench (it's important to note that you can't really compare data from flowbench to flowbench) a stock Y8 head flows about 190 cfm on the intake side and 160 cfm on the exhaust side. Moose has the Z6 info, which I'm sure he'll post once he sees this thread.

ryancivic2000
Registered User
Posts: 492
(6/4/03 12:48 pm)
Re: INTAKE MANI I guess you really can't compare flowbench to flowbench then, because if the Y8 does flow that much, according to Alaniz website's flow numbers the B18C5 and B16 flowed less than that.

kyosoeg6
Registered User
Posts: 5
(6/5/03 12:58 am)
z6 head or y8 head what im planning on doing is a balls out port job on a z6 head.the z6 flows better but does have a bigger cc.if u weld the ccs then u get the best of both worlds.the compression of the y8 and the flow charecteristics of the z6

Maxzee
Registered User
Posts: 111
(6/5/03 5:48 pm)
Re: z6 head or y8 head ryan, yes you're quite right about not being able to compare Alaniz' flowbench data to the numbers Moose and I got up here in Toronto (at Canadian Cylinder Head Technologies...a very reputable shop for head work and flowbenching).

On the other hand, here's the data I have for my ported Y8 head (intake) measured at unknown depth of H20:

.100 81cfm
.200 148cfm
.300 181cfm
.400 201cfm
.500 204cfm

I'm assuming that the shop we used measured cfm at a different test pressure (ie. different depth of water) than Joe Alaniz does. For a conversion table, go to www.alaniztechnologies.co...harts.html
I'll find out what test pressure was used to do our heads so that we can actually convert the data and make it a bit more comparable, but it is important to recognize that even after converting the data there is still some inherent variation flowbench to flowbench (just like with dynos). This being the case, the value of a flowbench (again, just like a dyno) isn't for comparing to other data produced on other flowbenches but instead to measure gains (or losses) made on a specific cylinder head on the same flowbench. As I'm sure you know, a flowbench is simply a tool used to gauge how much the porter has improved flow through the head so that he/she can refine their technique and extract maximum flow from the head through a process of testing-porting-testing-porting.

Edited by: Maxzee at: 6/5/03 5:51 pm

Thanks to all those who contributed in this discussion and provided the photos.

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